I recently got hold of a set of the new Severne Swats and am loving them!! The new Swat is a very different sail to the previous models. It seems to have a decent tuning range, giving it bottom end power but really good top end control, in a very stable 4 batten sail. On the wave it is really easy to control, reacting fast when you need the sail to depower/repower through the bottom to top turn. The sails are very light and have a slightly softer feel to the S1, which I find makes it easier to control the sail in the gusts and through maneuvers. The power from the sail comes in a feeling of lift and forward pull/acceleration, not a heavy back hand pull, making it also a great choice for lighter riders.
I have tried quite a few of the 2011 and 2012 wave sails from various 'top end' brands, and really would choose the Swat over most of them, especially when you consider the price!! Looking forward to summer 
I converted to SWATs last season and love them. The only draw back I would say is top end control, the '11's seems to get a bit wild when you got fairly overpowered. From the look of them and confirmed by your comments they have addressed this in the '12 model, not to mention they look a hell of a lot cooler.
Just took delivery of a '12 SWAT buts it's a 4.2 so It hasn't seen action yet. I decided to go an S1 for my biggest wave sail as I think overall it's a more controllable sail particularly in the larger sizes and a bit lighter (5.9, I use this sail for FS a lot). I'd upgrade my 4.7 and 5.2 but they aren't that old!
Personally going off even the '11 ones there is not a sail on the market that can get near the bang for your buck of a SWAT. The '12 model has stepped up in the looks/performance department but the cost still super low, maximum respect to Severne for putting out a sail like this. Personally I reckon if more people tried them they'd dominate the market, as you say I reckon they are a way better sail than almost everything else out there at basically half the price...
